The structure of modern industry has no choice but to be dependent on fossil fuels as most of the raw materials and energy sources in chemical engineering. The amount of fossil fuels is limited, and the use of fossil fuels causes various environmental problems as well as an economical problem. In such situations, research on novel renewable energy that can substitute for fossil fuels is progressing, and energy-generating technology using solar light corresponds to one of the ultimate energy technologies on which a human should depend. Light energy utilization, which is technology to convert light into chemical or electrical energy, can be implemented using various methods, and among these, in vivo photosynthesis has ended up with a current capability to utilize light after 3.5 billion-years of evolution.
Photosynthesis takes place in algae and various microorganisms as well as plants. Such photosynthesis is broadly classified into oxygenic photosynthesis and anoxygenic photosynthesis depending on the type of electron donor. The oxygenic photosynthesis takes place in plants, algae, cyanobacteria, etc., and is characterized by generating oxygen from water (H2O) as an electron donor. Such oxygenic photosynthesis occurs in a thylakoid membrane, which is a distinct membrane structure present in microorganism and chloroplast of plants and algae. Light energy excites electrons to induce a series of electron flow, and during such electron flow, protons are transferred through the membrane to form a proton concentration gradient between the inner and outer spaces of the membrane. As a result, the proton concentration gradient leads to the synthesis of adenosine triphosphate (ATP) through the action of ATP synthase. Also, such an electron flow is transferred to ferredoxin, and finally reduces nicotinamide adenine dinucleotide phosphate (NADP+) into a reduced form of nicotinamide adenine dinucleotide phosphate (NADPH). Here, the generated NADPH may be converted into a reduced form of nicotinamide adenine dinucleotide (NADH) by the action of pyridine nucleotide transhydrogenase (Pnt).
Anoxygenic photosynthesis is known to take place in purple non-sulfur bacteria, purple sulfur bacteria, green non-sulfur bacteria, green sulfur bacteria and Heliobacteria, and does not generate molecular oxygen during this process, unlike the oxygenic photosynthesis. Particularly, in purple non-sulfur bacteria, such a photosynthesis mechanism occurs in an intracytoplasmic membrane which is invaginated into the cell. In a reaction center present in the intracytoplasmic membrane of the bacteria, a photochemical reaction is initiated by light energy, thereby inducing cyclic electron transfer. ATP is synthesized from adenosine diphosphate (ADP) and inorganic phosphate by ATP synthase using a proton concentration gradient generated in this process as a driving force. However, when reverse electron flow in which protons are transferred in an opposite direction of the intracytoplasmic membrane takes place by complex I present therein, adenine dinucleotide (NAD+) is reduced into NADH. Afterward, quinone which has lost electrons obtains electrons again during the conversion of succinate into fumarate by the action of succinate dehydrogenase (complex II) also present in the intracytoplasmic membrane. NADH generated by such a mechanism may be converted into NADPH by the action of a pyridine nucleotide transhydrogenase like in oxygenic photosynthesis.
ATP and NAD(P)H serve as cofactors of enzymes mediating various in vivo biochemical reactions. Thus, in living body, continuous synthesis of ATP and NAD(P)H is needed, and enzyme reactions for producing such cofactors by consuming energy from various metabolic substances have been known. As representative examples, ATP and NADH are generated by the action of the related enzymes in glycolysis and citric acid (or TCA) cycle. Moreover, methods of synthesizing ATP and NAD(P)H for in vitro biochemical reactions have been known. For ATP synthesis, methods using creatine phosphate and creatine phosphokinase are known. Creatine phosphokinase mediates a reaction for ATP synthesis by transferring a phosphate group of the creatine phosphate to ADP. That is, this enzyme may synthesize ATP from ADP by consuming the creatine phosphate. Also, glucose-6-phosphate dehydrogenase mediates the reduction of NADP+ into NADPH by consumption of glucose-6-phosphate. However, when such reactions are practically applied to an in vitro enzyme reaction for producing a useful substance, the creatine phosphate or glucose-6-phosphate has to be continuously provided during reaction, resulting in a greatly increase of production cost with low practicality.
The invention disclosed in Korean Patent Application No. 10-2011-7017135 proposes that a separated composition for regenerating ATP may include a thylakoid membrane. However, for photophosphorylation in the thylakoid membrane to generate ATP, a proton concentration gradient is necessarily formed, and it may not be accomplished with a planar membrane, which is not a vesicle-type membrane by which inner and outer spaces are spatially separated. Actually, the above application does not present the result of generating ATP using the thylakoid membrane. Also, the above invention does not present a method of producing NAD(P)H using the thylakoid membrane, either.
In addition, the invention disclosed in Korean Patent Application No. 10-2008-0021127 is similar to the present invention in terms of the use of separated thylakoid membrane as an active component, but is different in that the invention is mainly characterized by presenting a method of controlling obesity by making a human feel satiety with an inhibitory component of thylakoid membrane against a pancreatic lipase.
The things that are described as the background art are merely provided to help in understanding the background of the present invention, and thus it should not be taken as an admission that they correspond to the conventional art previously known to those of ordinary skill in the art.